1. Field of the Invention
This application relates broadly to sound suppressors for firearms. More particularly, it concerns a cooling system for a firearm sound suppressor, and allows for the cooling of a firearm sound suppressor through the use of a cooling system attached to a firearm sound suppressor or being integral to a firearm sound suppressor.
2. Description of the Prior Art
Sound suppressors are intended to capture, cool and delay the exit of hot muzzle gases from a firearm. If the firearm sound suppressor is efficient in reduction of the discharge sound, the sound suppressor will experience an increase in temperature during firing as the longer the gases are retained within the suppressor, the higher the temperature of the suppressor. The temperature will also increase with the number of shots fired through the suppressor, and with the wide spread use of suppressed semi-automatic and automatic rifles, there are a number of problems that end users can face that are caused by the increase in temperature when firing occurs. When used with a semi-automatic or automatic rifle or machinegun, the temperature increases rapidly with the firing rate. Prolonged firing will result in structural damage and eventual failure unless the sound suppressor is constructed from high-temperature resistant metals such as stainless steels or other steel alloys like austenitic nickel-chromium based super alloys such as Inconel™.
These materials have drawbacks and these include increased weight, problems with machining, and cost compared to other steel alloys. Even using these materials, prolonged or extreme firing will eventually result in degradation of the structural integrity of the suppressor and failure of the suppressor itself. The high temperatures from such extreme firing i.e. continuous automatic fire of 400 or more rounds can contribute to the eventual failure. The continuous training schedules of anti-terrorist and military personnel means that suppressors used on their small arms are exposed to high round counts daily or weekly. The life span of some modern suppressors may be as short as 5-7000 rounds if used with short barreled automatic rifles while with other automatic rifles, the life span may be as high as 40-50,000 rounds, this being highly dependent upon the use of the sound suppressor.
The use of stainless steel alloys and austenitic nickel-chromium based super alloys has become popular with suppressor manufacturers to compensate for the use and abuse of suppressors by end-users such as anti-terrorist personnel and special military units. Even with the use of high strength steel alloys, machine gun suppressors require thicker internal structures to maintain strength at very high operating temperatures. With the drawbacks of increased weight and cost, some manufacturers have resorted to standard engineering practices such as thinning out the structures while at the same time attempting to maintain structural integrity. Some have used stamped thin metal baffles welded together to form an assembly. Some of these suppressors have been somewhat successful; others have not. Even with such super alloys, extreme usage will eventually result in component failure and temperature is a major factor in the failure of sound suppressor components. The retention of heat in the sound suppressor from multiple shots is a major problem with sound suppressors for use with short barreled automatic rifles, automatic rifles and machine guns.
Other current sound suppressors use titanium to help reduce weight but at the same time maintain structural integrity. Titanium has a very high strength-to-weight ratio and is currently being used to produce sound suppressors that are light in weight when compared to stainless steel or super alloys such as Inconel™. The main problem with titanium when used with sound suppressors is that while the weight factor is ideal, the suppressors are not suitable for use with automatic small arms such as assault rifles and machineguns. The main reason is that the heat from prolonged semi-auto or automatic fire results in eventual failure of the suppressor components in much the same manner as prolonged semi-automatic or automatic fire with stainless steel suppressors. The titanium suppressor will begin to fail at a much lower temperature than a stainless steel suppressor. A temperature of approximately 800 degrees F. for the titanium suppressor will start to result in failure while a temperature of approximately 1200 degrees F. will start to result in the failure of the stainless steel suppressor. While the reduced weight provides a large advantage, again it is prolonged semi-automatic or automatic firing that will eventually result in failure of the suppressor.
Another problem facing the users of sound suppressors, more so with suppressed sniper rifles, is that of heat mirage. Heat mirage is optical distortion caused by heat waves rising directly from the sound suppressor in front of the telescopic sight. After shooting in hot environments, this can cause the sniper to miss the target and this may be critical in military operations. Some shooters use mirage shields to minimize the effects of heat mirage but this means an extra piece of equipment to carry when in the field.
To reduce the temperature of the sound suppressor when used with small arms such as semi-automatic and automatic rifles, suppressed sniper rifles, and machineguns, it is proposed that a unique cooling system be used. This is ideally an integral part of a sound suppressor, though it may be retro-fitted to an existing sound suppressor or it may be a detachable system.
The present invention utilizes the firearm sound suppressor to act as a host for a cooling system that provides for cool ambient air to be drawn around the outer surface of the sound suppressor by the creation of a suction effect during the firing of the host firearm. A shroud is fitted over the outside or external surface of the sound suppressor and this shroud may extend for the entire length of the sound suppressor or may be shorter if so desired. An annular gap is created between the outside surface of the sound suppressor and inside surface of the shroud. At the distal or front end of the sound suppressor, a structure is positioned that provides a suction effect, and the shroud is attached to this structure. This structure is positioned forward of the front end and exit hole of the sound suppressor and a stand-off distance or space is created between the exit hole of the sound suppressor and the bore hole of the structure.
When the host firearm is discharged, the hot propellant gases expand into the sound suppressor and are then discharged from the sound suppressor at a greatly diminished pressure level and sound level. These pressurized gases expand forward into the space between the front end cap of the suppressor and the structure and upon discharging into the atmosphere through the structure, create a vacuum or ejector effect. The pressure of the discharging gases is more than sufficient to create a vacuum effect. This results in cool ambient air being sucked into the air gap or space between the outside of the sound suppressor and the inside of the shroud, at the rear end of the shroud, and then forward into the structure and then into the atmosphere through the structure. Even one or two shots fired from a bolt action rifle are sufficient to create the suction effect and provide cooling of the sound suppressor.
Small vanes may be provided to the cooling system to provide additional cooling and may also enhance the performance of the cooling structure by increasing the surface area for heat to be transferred from the suppressor to the cooling air flow. In one embodiment, the vanes may be positioned on the external surface of the sound suppressor with the shroud fitting closely over the vanes. This will provide an additional cooling effect by increasing the heat transfer from the sound suppressor to the shroud and hence to the atmosphere. To enhance the flow of the cool air around the outside surface of the sound suppressor, the vanes may be provided with a helical twist to induce motion in the flow of cool air being sucked forward and increase the mixing effectiveness of the cool air stream with the hot muzzle gases in the structure. In an alternate embodiment, the vanes may be positioned on the internal surface of the shroud, providing a spacing effect between the shroud plus structural integrity to the shroud as well as the additional cooling from the sound suppressor to the shroud.